Allow null pruning at depth 1

ajithcj · mcostalba · commit f2f3a06a1acf · 2016-07-24T09:54:07.000+02:00
This removes a check that prevents null pruning at depth 1 PLY.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 23445 W: 4638 L: 4521 D: 14286

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 61416 W: 8627 L: 8563 D: 44226

bench: 8145304
diff --git a/src/search.cpp b/src/search.cpp
@@ -729,7 +729,6 @@ namespace {
 
     // Step 8. Null move search with verification search (is omitted in PV nodes)
     if (   !PvNode
-        &&  depth >= 2 * ONE_PLY
         &&  eval >= beta
         && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY)
         &&  pos.non_pawn_material(pos.side_to_move()))
